Which of the following layers of skin lack blood vessels?
A.
Papillary
B.
Epidermis
C.
Reticular
D.
Hypodermis
The Correct Answer and Explanation is:
The correct answer is:
B. Epidermis
Explanation:
The skin is composed of three primary layers: the epidermis, dermis, and hypodermis (subcutaneous layer). Each layer has distinct characteristics and functions. Among these layers, the epidermis is the one that lacks blood vessels.
- Epidermis: This is the outermost layer of the skin. It provides a protective barrier and is primarily made up of keratinocytes, which produce the protein keratin. The epidermis also contains melanocytes (which produce pigment) and Langerhans cells (which are involved in immune responses). Although the epidermis is vital for protecting the body from environmental damage and infection, it does not contain blood vessels. Instead, it receives nutrients and oxygen through diffusion from the underlying dermis. This avascular nature helps in maintaining the barrier function without the complexity of blood vessels directly within it.
- Dermis: This layer lies beneath the epidermis and consists of two sub-layers—the papillary dermis and the reticular dermis. The dermis is rich in blood vessels, which supply nutrients to the epidermis and regulate body temperature through vasodilation and vasoconstriction. It also contains connective tissue, collagen, elastin, hair follicles, and glands.
- Hypodermis: Also known as the subcutaneous layer, the hypodermis is the deepest layer of the skin. It consists of loose connective tissue and fat cells. This layer serves as insulation and cushioning for the body, and it contains larger blood vessels and nerves that help in thermoregulation and sensation.
The avascular nature of the epidermis is crucial for its role in protecting the body from pathogens and physical damage while allowing for rapid regeneration and repair. The nutrients needed for the epidermis are provided by the vascularized dermis beneath it, ensuring that the epidermis can maintain its vital functions effectively.